I’m a complete beginner in this field; I would like to ask the experts here for advice on choosing an appropriate pump
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Background: There is a newly dug water body; currently, there is no water supply from the upstream area, so it is necessary to provide a water source for the upstream section by using a pump in the downstream area, with pipes connecting the pump to the upstream side. It is estimated that around 290 meters of pipes will be needed, with a height difference of about 3 meters. What size pump is required, and what material should the pipes be made of? There is also the relationship between the pressure difference at both ends of the pipe and the head difference; P=ρgH=ρg(H0-SQ2), where H0 is the head generated by the pump when the flow rate is 0, and this value is 1.2 times the rated head (as I found on the Internet) Both the outlet pressure P and the flow rate S are unknown; how can they be calculated? There is also the head loss along the pipeline, hf=SLQ2. The pump head H=hf+k*h=SLQ2+k*h. Is hf the same as P in the formula above? Is Q the rated flow rate or the effective flow rate? ； Is h the effective head? ； K is the air resistance, with a value of 1.1). Both of the formulas above were found on the Internet; they should be correct. I hope those who know more about this can help answer my questions
There are two best ways to address this problem: one is to master this subject, and I recommend getting a book on Principles of Chemical Engineering; the chapter on fluid transport in it will make things clear once you read it. These include the selection of pipe diameter, pipeline resistance, and pump selection. Following the solution method outlined in the book, start by drawing a schematic diagram. Then carry out the calculations as required by Bernoulli’s equation; it’s a bit complicated, but not difficult, so it’s worth giving it a try. The second option is to find a brand pump manufacturer or supplier, explain your situation clearly, and it’s best to attach a simple diagram. As long as you purchase their pumps, they will address these questions for you. It’s worth a try. It should be noted that they are responsible for the design, but not for the construction. Otherwise, he will design large-diameter pipes for you. For reference.
The design institute advises you: It’s actually quite simple – it comes down to flow rate, head, and pump type. 1. Calculation of flow rate: The flow rate refers to the amount required by the upstream system. If the upstream system needs 20 m3/h, it is advisable to include a margin, such as 22–24 m3/h. It’s determined by demand. 2. Calculation of head: A: First, it is necessary to calculate the pressure at the pump inlet. For example, if your pump is located below the water source, then the pressure at the pump inlet is the static pressure of the water minus the resistance loss in the inlet pipes. B: Calculation of the pressure required at the pump outlet: It depends on the pressure needed at the point of use. For ordinary drinking water, the pressure is generally below 0.4 Mpa; then, the pressure required to overcome a 3-meter resistance is added, along with the pressure needed to overcome frictional losses along the pipeline and local resistance. Add up the totals and then multiply by 1.1 to obtain the required outlet pressure. C: Subtract the outlet pressure, then divide by the density and 9.8 to get the head. 3. The K you mentioned is the amplification factor. It’s not air resistance; when fluid flows within a pipe, there is no air resistance. 4. As for the material of the pipes, PP pipes are recommended for water supply, while steel pipes are suitable; for sewage, PVC pipes or steel pipes are recommended. It mainly depends on the medium and purpose.
There are many versions, and they can generally be understood by people with a high school education level. Mastering this is essential in this industry. It’s worth a try.
Well, I’m not trained for drainage work, but since no one else in the company could do it, I was assigned to take on the task. I don’t know anyone who specializes in this field, so I had no choice but to look for information online. I’m quite lucky to have found this website; in the future, I’ll definitely consult these experts more often if I encounter any problems
Thank you so much for being so detailed! But there are still a few issues: 1. Flow rate (I have no idea what this means); different flow rates result in different effects, and I also don’t know how to determine the flow rate based on specific requirements, such as for my project. The area upstream of the landscape river is about 5 meters wide – how can I estimate the flow rate in that case? ； 2: Head: A, the pressure at the pump inlet. In the example you gave, the pump is located below the water surface; if my pump is above the water surface, then the pressure at the pump inlet should be the static pressure of the water plus the resistance losses in the inlet pipes. Regarding the pressure at point B, I saw that others use a pressure of 0.25 for sprinkler irrigation; since I’m supplying water to a small river, does the pressure need to be higher? ； 4 pipes, UPVC was used; I’m not sure if it was the right choice
Suppose I need a flow rate of 50 m3/h. The pump is located 1 meter above the water surface, and the pipe from the pump’s inlet to the water surface is 4.5 meters long (with 0.5 meters of the pipe extending underwater). The roughness coefficient for this pipe, based on PE pipe standards, is 0.01, and its inner diameter is 0.095 meters. The inlet pressure P_in can be calculated as follows: P_in = ρgh1 – SLQ2 = 1000*9.8*1/1000 – 289*0.0142*5 = 0.7 MPa. The outlet pressure P_out is given by: P_out = (0.4 + 289*0.0142*3 + 289*0.0142*290)*1.1 = 18.7 MPa. Therefore, the pressure difference P = P_out – P_in = 18 MPa. The head H can be calculated as: H = P/ρg = 18000/(1000*9.8) = 18.367 meters. The flow rate is then: Flow rate = √(H/(S*L)) = 0.0147 M/s, which corresponds to a flow rate of 52.92 m3/h when converted to per hour. Based on these results, a pump with a flow rate of 60 m3/h and a head of 20 meters should be selected. Note: The current length of the pipeline from the water pump outlet to the end of the pipeline is 290 meters, and the height difference between the water intake point and the point where water is needed is 3 meters. The local resistance in the outlet pressure has not been taken into account. These are the results I have calculated; I hope someone who is knowledgeable can help check whether these calculations are correct
I’ve learned about it, but personally I think it’s better to go straight to a store that sells water pumps (preferably a reputable, experienced one), explain your requirements to them, and refuse to pay if those requirements aren’t met. That way, everything is taken care of. Theoretical knowledge is certainly important, but practical knowledge is just as essential. It’s impossible for any of us to be a jack of all trades
1. First, determine the maximum flow rate of the pump based on the requirements； 2. Then determine the pipeline specification (inner diameter) based on investment constraints and the available pipelines ； 3. The flow rate divided by the inner diameter of the pipeline gives the maximum flow velocity in the pipeline ； 4. Based on the flow velocity, the head loss is calculated as: friction loss + local losses + height difference = head pressure ； 5. The calculated head is increased by a safety margin (around 1.2–1.3) to obtain the final pump head ； 6. Select the pump based on its flow rate and head.
The water pump manufacturer’s WeChat ID is 18032233998, which is the same as their phone number